Analysis of the cell interior at molecular level is the subject of growing interest. Several probes and antibodies have recently appeared which are used in research as well as routinely and are directed against intracellular structures. These probes and antibodies, because of their macromolecular character, cannot penetrate into the cell through the cellular membrane by themselves. Treatment of the cells is therefore necessary to render the cellular membrane permeable (permeabilization stage). This treatment causes an important modification of the exterior lipid membrane and can, depending on the method used, lead to a loss of the cell morphology, or even a loss of the entire cell.
A standard permeabilization method consists of a treatment of the cells on a microscope slide or in suspension, with dilutions of alcohols at low temperature (−20° C.). This method has the advantage that the molecular structures and the intracellular target antigens are well preserved. But in addition to the complicated procedure, and the low temperature used, the cell morphology is substantially modified at the end of treatment.
Several permeabilization methods use a fixation of the cells by chemical modification of the proteins using aliphatic aldehydes leading to cross-linking and aggregation of the proteins. The permeabilization is obtained by a treatment with an alcohol or a surfactant. The fixation by aliphatic aldehydes is especially known for its good preservation of the cell morphology after permeabilization. However, at protein molecular level, many antigen sites are destroyed by the fixation methods.
Reagents for permeabilizing the cells are more commonly found in the groups of organic solvents, alcohols, weak bases and weak acids. These reagents permeabilize the cellular membrane, however they do not generally stabilize the cell morphology.
It is therefore desirable to have a reagent for permeabilization of cells, which protects the cell morphology after permeabilization and does not modify the antigen sites inside and outside the cell.